Multi-layer multi-weld joint re-arcing welding method

Abstract

The invention relates to the technical field of welding, and discloses a multi-layer multi-weld joint re-arcing welding method, which comprises the following steps of: determining an arcing parameter according to a welding position, keeping a first included angle between a welding wire and a welding direction before arcing, and forming an arc crater; when arcing is conducted again, the position, 0.1 mm-20 mm away from the outer arc edge of the arc crater, around the arc crater serves as an arcing point, and normal welding is conducted after a molten pool is fused and crosses the arc crater, the point, 0.1 mm-20 mm away from the outer arc edge of the arc crater, of the arc crater serves as the arcing point, due to the natural shrinkage effect when the molten pool is solidified, welding slag and oxide are extruded to the bottom of the arc crater, and therefore the arc crater is welded normally. The bare metal exposure rate can reach more than 95%, a welding slag coverage area with poor conductivity is effectively avoided, and the arc stability is greatly improved; the retention time of a molten pool is prolonged, gas escape is promoted, pore defects are reduced, and the molten drop size qualification rate is increased; the method does not need mechanical polishing pretreatment, can be directly applied to complex scenes such as laser arc hybrid welding, limited space and underwater welding, greatly reduces the repair rate, and shortens the construction period of an engineering project.

Description

Technical Field

[0001] The present invention relates to the field of welding technology, and particularly to a multi-layer and multi-pass weld restart arc welding method. Background Art

[0002] During the welding process, arc stopping refers to the operation of actively extinguishing the arc due to reasons such as wire depletion, position determination, or completion of phased operations. The restart arc joint is a key step in reigniting the arc and connecting it to the original weld, and its quality directly affects the overall welding strength. For example, in traditional multi-layer and multi-pass CO2 shielded arc welding, the general process is to start the arc at a position 10 mm - 20 mm in front of the crater, and achieve fusion by pulling back to the stopped arc crater and using a crescent, sawtooth, or circular bead oscillation method. However, there are various defects in actual operation.

[0003] Research shows that the conductivity of the slag-covered area is only 30% - 50% of that of the bare metal. Welding in this area will reduce the arc stability. Even if the slag-covered area is pretreated by mechanical grinding, the newly formed oxide film and residual grinding sparks in the high-temperature environment will still deteriorate the conductivity. Especially when starting the arc with a large current (above 260 A), the molten pool is formed instantaneously, which is difficult to control, and easily leads to problems such as poor fusion and oversized droplet size, and further causes defects such as appearance mutation, point-like lack of fusion, and slag inclusion. In complex working conditions, such as inside a building steel structure box column or underwater welding scenarios, tools such as angle grinders cannot be used due to space limitations or water flow scouring, and the welder's experience becomes the only reliance for quality control, resulting in fluctuations in welding quality. More seriously, the repair work will extend the construction period of projects such as high-altitude welding of large bridges by 30% - 50%. Summary of the Invention

[0004] In view of this, the present invention provides a multi-layer and multi-pass weld restart arc welding method to solve the problem of poor arc stability when restarting the arc at the weld.

[0005] The present invention provides a multi-layer and multi-pass weld restart arc welding method, including:

[0006] Determine the arc stopping parameters according to the welding position. Before arc stopping, keep the welding wire at a first included angle with the welding direction and form a crater;

[0007] When restarting the arc, use the position around the crater and 0.1 mm - 20 mm away from the outer arc edge of the crater as the starting point. After the molten pool fuses and crosses the crater, switch to normal welding.

[0008] Optionally, when restarting the arc, select the position 2 mm above the crater and away from the outer arc edge of the crater as the starting point.

[0009] Optionally, the value range of the first included angle is 80° - 90°.

[0010] Optionally, when the welding position is flat welding, the arc extinguishing parameters are set to 70%-80% of the normal welding parameters.

[0011] Optionally, when the welding position is flat welding, at the restart of arc, the welding torch forms an angle of 80°-90° with the welding direction and an angle of 80° with the inner side of the weld seam.

[0012] Optionally, when the welding position is horizontal welding, the arc extinguishing parameters are 60%-70% of the normal welding parameters.

[0013] Optionally, when the welding position is horizontal welding, at the restart of arc, the welding torch forms an angle of 80°-90° with the welding direction and an angle of 70° with the lower side of the weld seam.

[0014] Optionally, when the welding position is fillet welding, the arc extinguishing parameters are 70%-80% of the normal welding parameters.

[0015] Optionally, when the welding position is fillet welding, at the restart of arc, the welding torch forms an angle of 80°-90° with the welding direction and an angle of 30° with the lower side of the weld seam.

[0016] Optionally, ensure that there is no ball formation at the end of the welding wire before starting the arc.

[0017] Beneficial effects

[0018] The multi-layer and multi-pass weld restart arc welding method provided by the present invention includes determining the arc extinguishing parameters according to the welding position, keeping the welding wire at a first angle with the welding direction before arc stopping and forming an arc crater; at the restart of arc, taking the position around the arc crater and 0.1 mm - 20 mm away from the outer arc edge of the arc crater as the starting arc point, and turning to normal welding after the molten pool fuses and crosses the arc crater.

[0019] The multi-layer and multi-pass weld restart arc welding method provided by the present invention selects the point 0.1 mm - 20 mm away from the outer arc edge of the arc crater as the starting arc point. Due to the natural shrinkage effect during the solidification of the molten pool, the welding slag and oxides are extruded to the bottom of the arc crater, and the exposure rate of bare metal can reach more than 95%, effectively avoiding the welding slag coverage area with poor conductivity and greatly improving the arc stability; this method does not rely on mechanical grinding pretreatment and can be directly applied in complex scenarios such as laser-arc hybrid welding, confined space and underwater welding, greatly reducing the repair rate, shortening the project construction period, and at the same time effectively solving the defect problems such as appearance mutation, point-like lack of fusion and slag inclusion caused by traditional processes, so that the strength of the overall welded joint exceeds the base metal standard. Description of the drawings

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0021] Figure 1 It is a schematic structural diagram of the starting arc point position when the welding position in the embodiment of the present invention is flat welding;

[0022] Figure 2 It is a schematic structural diagram of the starting arc point position when the welding position in the embodiment of the present invention is horizontal welding;

[0023] Figure 3 It is a schematic structural diagram of the starting arc point position when the welding position in the embodiment of the present invention is fillet welding;

[0024] Explanation of reference numerals:

[0025] 1. Starting arc point. Specific embodiments

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0027] The following combines Figures 1 to 3 , and describes the embodiments of the present invention.

[0028] According to an embodiment of the present invention, taking gas shielded welding as an example here, a method for restarting arc welding of multi-layer and multi-pass welds is provided, including:

[0029] Determine the arc extinguishing parameters according to the welding position. Before arc extinguishing, keep the welding wire at a first included angle with the welding direction and form an arc crater;

[0030] When restarting the arc, take the position around the arc crater and at a distance of 0.1 mm - 20 mm from the outer arc edge of the arc crater as the starting arc point 1, and turn to normal welding after the molten pool fuses and crosses the arc crater.

[0031] It should be noted that multi-pass welding refers to a welding process for thick plates or large groove welds that is completed by welding in layers and passes. Multi-pass welding fingers are stacked in layers along the thickness of the weld. After each pass, slag must be cleaned and the interpass temperature must be controlled. Multi-pass welding fingers fill the groove by arranging multiple passes in parallel within the same layer. The pass sequence must be planned to avoid slag inclusion or lack of fusion.

[0032] Specifically, arc cessation utilizes a four-step on-off control method. This method includes the following steps: First, briefly press and immediately release the torch trigger, continuing normal welding with the welding current. Maintaining a stable wire feed and a normal welding current is essential before arc cessation. Second, briefly press and immediately release the torch trigger to complete arc cessation, reducing the wire feed speed and utilizing a slightly higher voltage to quickly create a distinct arc crater in the weld pool. This process, involving four presses of the torch trigger, is known as the four-step on-off control method. This precise control of the arc cessation process, combined with wire angle optimization, creates a regular arc crater, laying the foundation for restarting the arc.

[0033] It should be noted that flat welding, horizontal welding, and fillet welding are three typical welding positions. Flat welding refers to welding with the weld axis in a horizontal position and the welding direction being horizontal or nearly horizontal. The molten pool relies primarily on surface tension to maintain its shape. Horizontal welding refers to welding with the weld axis in a vertical position and the welding direction being horizontal. The molten pool is susceptible to gravity and may fall. Fillet welding refers to welding performed at the joint between two workpieces at a certain angle.

[0034] Specifically, the welding gun angle needs to be determined according to the welding position, and then the welding gun is moved using an S-shaped path to ensure that the molten pool is fully fused and passes over the arc crater. The S-shaped path of the welding gun refers to the flattened wavy movement of the welding gun along the horizontal plane. The S-shaped path is elongated in the direction of the weld axis, and the lateral swing amplitude is narrowed, forming a continuous movement pattern similar to a wave line. The extended axial movement ensures that the arc is fully preheated to the arc starting point 1, and the small lateral swing promotes the gradual fusion of the new and old molten pools, avoiding the sudden advance of the molten pool under high current, and the wavy continuous movement produces periodic heat input fluctuations, which is conducive to the discharge of gas and impurities. Compared with the traditional inverted crescent-shaped wire movement, the S-path can reduce the oscillation amplitude of the molten pool by 40% at high current, thereby improving the joint quality during high-line energy welding.

[0035] It is easy to understand that under high current conditions, the progressive fusion mechanism formed by the S-shaped path of the gun prolongs the residence time of the molten pool, promotes gas escape, reduces porosity defects, and improves the qualified rate of droplet size.

[0036] It should be noted that the specific location of the arc starting point 1 can be selected according to the specifications of the welded steel plate or the welding experience of the welding operator.

[0037] It should be noted that when the electric arc passes through the crater position, normal welding is carried out according to the conventional welding process and the method of moving the electrode. According to the specific requirements of the weld, linear, crescent, sawtooth, circular and other electrode moving methods can be selected, and a stable welding speed and angle should be maintained to obtain a good weld formation.

[0038] For the multi-layer and multi-pass weld restart arc welding method provided in this embodiment, a point at a distance of 0.1 mm - 20 mm from the outer arc edge of the crater is selected as the starting point 1. Due to the natural shrinkage effect during the solidification of the molten pool, the welding slag and oxides are extruded to the bottom of the crater, and the exposure rate of the bare metal can reach more than 95%, effectively avoiding the slag-covered area with poor conductivity and greatly improving the arc stability; this method does not need to rely on mechanical grinding pretreatment and can be directly applied in complex scenarios such as laser-arc hybrid welding, confined space and underwater welding, greatly reducing the repair rate, shortening the project duration, and effectively solving the problems of appearance mutation, point-like lack of fusion and slag inclusion caused by traditional processes, making the strength of the overall welded joint exceed the base metal standard.

[0039] Furthermore, when restarting the arc, a point 2 mm above the crater and at a distance from the outer arc edge of the crater is selected as the starting point 1.

[0040] It is easy to understand that by positioning the restart arc point 1 at 2 mm above the upper end of the outer arc edge of the crater, this area is in the transition zone between the slag-covered area and the pure metal, avoiding both the oxide layer with poor conductivity (the conductivity is only 30% - 50% of the bare metal) and retaining enough heat-affected zone of the base metal, so that the conductivity at the moment of starting the arc is increased to more than 85%;

[0041] Furthermore, the value range of the first included angle is 80° - 90°.

[0042] It is easy to understand that when the first included angle is controlled within the range of 80° - 90°, this nearly vertical angle can ensure that the arc force acts directly on the bottom of the molten pool, increasing the penetration depth, and at the same time avoiding the arc drift phenomenon caused by too small an angle; the large-angle configuration moves the contact point between the wire end and the molten pool backward, forming a longer arc protection area, effectively reducing the interference of the surrounding air on the welding process and improving the gas protection effect during restarting the arc.

[0043] Furthermore, when the welding position is flat welding, the arc extinguishing parameters are set to 70% - 80% of the normal welding parameters.

[0044] Specifically, when the welding position is flat welding, the normal welding parameters are a current of 320 A and a voltage of 35.5 V.

[0045] It is easily understandable that by adopting stepped arc-extinguishing parameter control and reducing the welding current and voltage in the arc-extinguishing stage to 70%-80% of the normal value (i.e., current 224-256A, voltage 24.9-28.4V) respectively, the temperature of the molten pool can be reduced to form an obvious crater.

[0046] It should be noted that the specific selection of the arc-extinguishing parameters can be made according to the specifications of the welded steel plate or the welding experience of the welding operator.

[0047] Furthermore, after the arc-extinguishing voltage is greater than 70%-80% of the normal welding voltage, an additional 1V is set.

[0048] It is easily understandable that by additionally increasing the current setting by 1V, the arc stability can be improved, effectively ensuring that there is no excessive weld metal at the crater, which is beneficial to effective fusion during restarting the arc joint and improving the success rate of restarting the arc.

[0049] Furthermore, when the welding position is flat welding, when restarting the arc, the welding torch forms an 80°-90° angle with the welding direction and an 80° angle with the inner side of the weld.

[0050] It is easily understandable that by adopting the composite angle control of an 80°-90° welding direction angle and an 80° weld inner side angle in the flat welding position, the arc force realizes three-dimensional optimized distribution. The large pushing angle ensures stable penetration, and the lateral 80° angle maintains the balance of the molten pool, preventing metal drift and ensuring edge fusion, making a smooth transition between multi-layer weld beads and significantly improving the welding quality and forming consistency.

[0051] Further, when the welding position is horizontal welding, the arc-extinguishing parameters are 60-70% of the normal welding parameters.

[0052] Specifically, when the welding position is horizontal welding, the normal welding parameter current is 280A and the voltage is 31V.

[0053] It is easily understandable that by adopting stepped arc-extinguishing parameter control and reducing the welding current and voltage in the arc-extinguishing stage to 60%-70% of the normal value (i.e., current 168-196A, voltage 18.6-21.7V) respectively, the temperature of the molten pool can be reduced to form an obvious crater.

[0054] Furthermore, after the arc-extinguishing voltage is greater than 60%-70% of the normal welding voltage, an additional 1V is set.

[0055] It is easily understandable that by additionally increasing the current setting by 1V, the arc stability can be improved, effectively ensuring that there is no excessive weld metal at the crater, which is beneficial to effective fusion during restarting the arc joint and improving the success rate of restarting the arc.

[0056] Furthermore, when the welding position is horizontal welding, during restarting the arc, the welding torch forms an angle of 80°-90° with the welding direction and an angle of 70° with the lower side of the weld seam.

[0057] Understandably, when restarting the arc at the horizontal welding position, a combined angle control is adopted where the welding torch forms an angle of 80°-90° with the welding direction and an angle of 70° with the lower side of the weld seam, enabling a three-dimensional optimized distribution of the arc force. The large angle in the welding direction ensures stable advancement of the arc and sufficient penetration depth, while the 70° lower side angle forms an upward supporting force, effectively resisting the downward trend of the molten pool metal, making the weld bead formation more uniform and regular. At the same time, it promotes good fusion between the weld bead and the base material, improving the formation quality and joint performance of multi-layer welding at the horizontal welding position.

[0058] Further, when the welding position is fillet welding, the arc extinguishing parameters are 70%-80% of the normal welding parameters.

[0059] Specifically, when the welding position is fillet welding, the normal welding parameters are a current of 320A and a voltage of 34.5V.

[0060] Understandably, by adopting a stepped arc extinguishing parameter control and reducing the welding current and voltage in the arc extinguishing stage to 70%-80% of the normal values (i.e., current 224 - 256A, voltage 24.15 - 27.6V) respectively, the temperature of the molten pool can be reduced to form an obvious crater.

[0061] It should be noted that the specific selection of the arc extinguishing parameters can be made according to the specifications of the welded steel plate or the welding experience of the welding operator.

[0062] Furthermore, the arc extinguishing voltage is set to increase by 1V after being greater than 70%-80% of the normal welding voltage.

[0063] Understandably, by additionally increasing the current setting by 1V, the arc stability can be improved, effectively ensuring that there is no excessive weld metal at the crater, which is beneficial for effective fusion during restarting the arc at the joint and improving the success rate of restarting the arc.

[0064] Further, when the welding position is fillet welding, during restarting the arc, the welding torch forms an angle of 80°-90° with the welding direction and an angle of 90° with the lower side of the weld seam.

[0065] Understandably, when restarting the arc at the fillet welding position, a precise angle combination where the welding torch forms an angle of 80°-90° with the welding direction and an angle of 90° with the lower side of the weld seam is adopted, enabling a three-dimensional optimized distribution of the arc force. The advancing angle of 80°-90° ensures that the arc stably penetrates into the root of the weld seam, while the 90° vertical angle generates a uniform lateral cladding force, effectively balancing the unique metal diversion phenomenon at the fillet welding position, ensuring full formation at the weld leg and avoiding undercut defects, improving the fusion quality and structural strength of the fillet weld.

[0066] Further, ensure that there is no ball formation at the end of the welding wire before arc starting.

[0067] Understandably, strictly check and ensure that there is no ball formation at the end of the welding wire before arc starting, so that the arc is stable and the energy is concentrated instantaneously at arc starting, avoiding problems such as spatter or poor conductivity caused by the molten ball at the end, and ensuring the quality consistency between the arc starting area of the weld seam and the normal weld bead.

[0068] Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations fall within the scope defined by the appended claims.

Claims

1. A method for restarting arc welding of multi-layer and multi-pass welds, characterized in that, Including: Determine the arc-extinguishing parameters according to the welding position. Before arc extinguishing, keep the welding wire at a first included angle with the welding direction and form an arc crater. When restarting the arc, take the position around the arc crater and 0.1 mm - 20 mm away from the outer arc edge of the arc crater as the starting point (1). Wait until the molten pool fuses and crosses the arc crater, then switch to normal welding.

2. The multi-layer multi-pass weld restart arc welding method according to claim 1, characterized in that When restarting the arc, select the position 2 mm above the arc crater and away from the outer arc edge of the arc crater as the starting point (1).

3. The method for restarting arc welding of the multi-layer multi-pass weld according to claim 2, characterized in that, The value range of the first included angle is 80° - 90°.

4. The multi-layer and multi-pass weld restart arc welding method according to any one of claims 1-3, characterized in that When the welding position is flat welding, the arc-extinguishing parameters are set to 70% - 80% of the normal welding parameters.

5. The method for restarting arc welding of a multi-layer and multi-pass weld according to claim 4, characterized in that When the welding position is flat welding, when restarting the arc, the welding torch forms an 80° - 90° included angle with the welding direction and an 80° included angle with the inner side of the weld.

6. The multi-layer multi-pass weld restart arc welding method according to any one of claims 1-3, characterized in that When the welding position is horizontal welding, the arc-extinguishing parameters are 60% - 70% of the normal welding parameters.

7. The method for restarting arc welding of a multi-layer and multi-pass weld according to claim 6, characterized in that When the welding position is horizontal welding, when restarting the arc, the welding torch forms an 80° - 90° included angle with the welding direction and a 70° included angle with the lower side of the weld.

8. The multi-layer multi-pass weld restart arc welding method according to any one of claims 1-3, characterized in that, When the welding position is fillet welding, the arc-extinguishing parameters are 70% - 80% of the normal welding parameters.

9. The multi-layer multi-pass weld restart arc welding method according to claim 8, characterized in that, When the welding position is fillet welding, when restarting the arc, the welding torch forms an 80° - 90° included angle with the welding direction and a 30° included angle with the lower side of the weld.

10. The multi-layer multi-pass weld restart arc welding method according to any one of claims 1-3, characterized in that, Ensure that there is no ball formation at the end of the welding wire before starting the arc.

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